Conventionally, for minimizing a semiconductor package, a multi-chip package structure has been used, in which a plurality of semiconductor chips is mounted in a single package to improve the packaging density. One type of such a multi-chip package structure is a three-dimensional package, in which a plurality of semiconductor chips is layered in a vertical direction.
However, according to such a three-dimensional package structure, in which a plurality of semiconductor chips is layered in a vertical direction, it might become difficult to radiate heat generated in the package if the number of semiconductor chips in the package is increased.
In that situation, for example, as shown in Patent Related Publication 1, a semiconductor package includes a heat transferable conductive sheet, provided between semiconductor chips, in order to radiate heat generated at the semiconductor chips. In the fourth embodiment of the patent related publication 1, it is described a heat transferable conductive sheet 38, which includes an approximately rectangle shield portion 38m, lead portions 38n, 38n . . . , extending from the four corners of the shield portion 38m to be connected to a substrate 35. Heat generated at a lower layer semiconductor chip 36 and an upper layer semiconductor chip 37 are transferred via connecting portions to the heat transferable conductive sheet 38, and radiated through the shield portion 38m, lead portions 38n, 38n, . . . and a ground wire 35b. 
[Patent Related Publication 1] 2004-111656A
However, according to the conventional technology shown in the above described publication, an sufficient extent of heat may not be radiated when the number of layers in a semiconductor package is increased.
Objects, advantages and novel features of the present invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.